Cho \(\dfrac{\overline{ab}+\overline{bc}}{a+c}=\dfrac{\overline{bc}+\overline{ca}}{b+c}=\dfrac{\overline{ca}+\overline{ab}}{c+a}\)
CMR : a = b = c
Cho:\(\dfrac{a+\overline{bc}}{\overline{abc}}=\dfrac{b+\overline{ca}}{\overline{bca}}=\dfrac{c+\overline{ab}}{\overline{cab}}\)
CMR:\(\overline{\dfrac{bc}{a}=\dfrac{\overline{ca}}{b}=\dfrac{\overline{ab}}{c}}\)
Cho \(\dfrac{a+\overline{bc}}{\overline{abc}}=\dfrac{b+\overline{ca}}{\overline{bca}}=\dfrac{c+\overline{ab}}{\overline{cab}}\). Chứng minh rằng \(\dfrac{\overline{ab}}{c}=\dfrac{\overline{ca}}{b}=\dfrac{\overline{bc}}{a}\)
cho \(\dfrac{\overline{abc}}{\overline{bc}}=\dfrac{\overline{bca}}{\overline{ca}}=\dfrac{\overline{cab}}{\overline{ab}}\). Tính \(\dfrac{a}{\overline{bc}}+\dfrac{b}{\overline{ca}}+\dfrac{c}{\overline{ab}}\)
Cho biết \(\dfrac{\overline{abc}}{\overline{bc}}=\dfrac{\overline{bca}}{\overline{ca}}=\dfrac{\overline{cab}}{\overline{ab}}\)
Tính tổng\(\dfrac{a}{\overline{bc}}+\dfrac{b}{\overline{ca}}+\dfrac{c}{\overline{ab}}\)
Cho tỉ lệ thức \(\dfrac{\overline{abc}}{a+\overline{bc}}=\dfrac{\overline{bca}}{b+\overline{ca}}\). CMR tỉ lệ thức \(\dfrac{a}{\overline{bc}}=\dfrac{b}{\overline{ca}}\)
Cho:\(\dfrac{\overline{ab}}{b}=\dfrac{\overline{bc}}{c}=\dfrac{\overline{ca}}{a}\)
CMR(\(\overline{abc}\))123=111123\(\cdot a^{40}\cdot b^{41}\cdot c^{42}\)
Ta có:
\(\dfrac{\overline{ab}}{b}=\dfrac{\overline{bc}}{c}=\dfrac{\overline{ca}}{a}\)
\(\Rightarrow\dfrac{10a}{b}+\dfrac{b}{b}=\dfrac{10b}{c}+\dfrac{c}{c}=\dfrac{10c}{a}+\dfrac{a}{a}\)
\(\Rightarrow\dfrac{10a}{b}+1=\dfrac{10b}{c}+1=\dfrac{10c}{a}+1\)
\(\Rightarrow\dfrac{10a}{b}=\dfrac{10b}{c}=\dfrac{10c}{a}\)
Áp dụng tính chất dãy tỉ số bằng nhau, ta có:
\(\dfrac{10a}{b}=\dfrac{10b}{c}=\dfrac{10c}{a}=\dfrac{10a+10b+10c}{b+c+a}=\dfrac{10\left(a+b+c\right)}{a+b+c}=10\)
\(\Rightarrow\left\{{}\begin{matrix}10a=10b\\10b=10c\\10c=10a\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a=b\\b=c\\c=a\end{matrix}\right.\Rightarrow a=b=c\)
\(\Rightarrow\left(\overline{abc}\right)^{123}=\left(\overline{aaa}\right)^{123}\)(1)
\(\Rightarrow c=111^{123}.a^{40}.a^{41}.a^{42}=111^{123}.a^{123}=\left(111.a\right)^{123}=\left(\overline{aaa}\right)^{123}\)(2)
Từ (1) và (2) suy ra: \(\left(\overline{abc}\right)^{123}=111^{123}.a^{40}.b^{41}.c^{42}\)
cho các số cs 2 chữ số \(\overline{ab}\) ,\(\overline{bc}\) thỏa mãn \(\dfrac{\overline{ab}}{\overline{bc}}\) =\(\dfrac{b}{c}\) (c\(\ne0\) )
c/mr:\(\dfrac{a^2+b^2}{b^2+c^2}\) =\(\dfrac{a}{c}\)
=>\(\dfrac{10a+b}{10b+c}=\dfrac{b}{c}\)
=>10ac+bc=10b^2+bc
=>ac=b^2
=>a/b=b/c=k
=>a=bk; b=ck
=>a=ck^2; b=ck
\(\dfrac{a^2+b^2}{b^2+c^2}=\dfrac{c^2k^4+c^2k^2}{c^2k^2+c^2}=k^2\)
\(\dfrac{a}{c}=\dfrac{ck^2}{c}=k^2\)
=>\(\dfrac{a^2+b^2}{b^2+c^2}=\dfrac{a}{c}\)
4. Cho tỉ lệ thức \(\dfrac{\overline{ab}}{\overline{bc}}\) = \(\dfrac{a}{c}\), CMR \(\dfrac{\overline{abbb...b}}{\overline{bbb...bc}}\) = \(\dfrac{a}{c}\)(1) với n - 1 số b và n ϵ N*.
Gíup mình với cảm ơn các bạn nhiều!!!
Áp dụng tính chất dãy tỉ số bằng nhau ta có:
\(\dfrac{\overline{ab}}{\overline{bc}}=\dfrac{a}{c}\Rightarrow\dfrac{10a+b}{10b+c}=\dfrac{a}{c}=\dfrac{9a+b}{10b}\\ =\dfrac{111...11\left(9a+b\right)}{111...11.10b}\)(có n chữ số 1 trong 111...11)
\(\dfrac{999...99a+111...11b}{111.110b}\\ =\dfrac{999...99a+a+111...11}{111.10b+c}=\dfrac{abbb...bb}{bbb...bc}=\dfrac{a}{c}\)(đpcm)
Cho \(\dfrac{\overline{ab}}{\overline{bc}}=\dfrac{a}{c}\). Cmr : \(\dfrac{\overline{abbb...b}}{\overline{bbb...bc}}=\dfrac{a}{c}\)
( n-1 chữ số b ở cả tử và mẫu )
Với số lượng chữ b ở tử và mẫu như nhau, ta có:
(abbb...b) / (bbb...bc)
= (a/c) . (bb...b / bb...b)
= (a/c) . 1
= a/c (đpcm)